Sometimes, it may, for example, be desirable to be able to mix hydraulic binders, while still in the dry state, with organic silicon compounds, even before the binders have been delivered to the consumer without the consumer having difficulties when the binders are further processed because of the presence of the organic silicon compounds. For this reason, it is desirable to provide powders which are redispersible in water and contain at least 30 percent by weight, based on the weight of the powders, of at least one organic silicon compound, in which at least 50 percent by weight of the organic silicon compound(s) used in preparing these powders are liquid or solid at room temperature at 1,020 hPa (abs.) and also contain hydrogen which is bonded directly to a silicon atom and/or condensable groups.
Powders that are redispersible in water and contain a water-soluble polymer and organic silicon compounds are described in U.S. Pat. No. 3,210,208 to Grass et al. This reference does not, however, disclose organic silicon compounds containing condensable atoms or groups.
Mixtures containing a water-soluble polymer and an organic silicon compound containing condensable groups are described in EP-PS No. 53 223 (published on 9th June, 1982, M. Roth et al, Wacker-Chemie GmbH). However, this reference does not disclose a process where the powder may be recovered by spraying-drying.
Even though these references disclose powders containing a water-soluble polymer and an organic silicon compound, it is unexpected and unobvious that aqueous emulsions or suspensions of compounds containing condensable and/or hydrolyzable substituents could be spray-dried at relatively high temperatures to provide usable products.
It is, therefore an object of the present invention to provide powders which are readily dispersible in water. Another object of the present invention is to provide powders which are redispersible in water which contain a water-soluble polymer and at least one organic silicon compound. Another object of the present invention is to provide a process for preparing powders which can be redispersed in water. Still another object of the present invention is to provide a process for preparing usable powders from an aqueous emulsion or suspension of compounds containing condensable and/or hydrolyzable substituents. A further object of the present invention is to provide a process for preparing aqueous redispersible powders which contain a water-soluble polymer and at least one organic silicon compound.